Great then, that means I don't have to go to Canadian Tire today to buy some metal polish that was used in your guide.

Nope.

(It was actually car polish, BTW)

Plus, it will usually end up pretty shiny when you get to the finer grits of sandpaper.

The most important thing is to use a flat surface and take your time. Especially when lapping the TRUE, to make sure that it slides easily. The water with dish soap helps with that. Also, don't apply too much pressure. Just use the weight of the heatsink.